In conventional cellular telecommunications networks, the activation of a subscriber identification module (SIM) requires that certain preconditions are met. Of particular interest here, the SIM must be associated with a unique telephone number (MSISDN). This familiar telephone number is generally used by a calling party wishing to make a voice (or video) call to the mobile terminal into which the SIM has been inserted. Invariably, the telephone number is selected (either automatically or in some instances by the user themselves) from a range of available Mobile Subscriber Integrated Services Digital Network (MSISDN) numbers owned by the provisioning operating company and the selected number is assigned to the SIM when the SIM is addressed for the first time by the operating company network: generally this means that the telephone number must be assigned before a user first activates the SIM under a prepay or contract arrangement.
The network operator bears a cost associated with provisioning a SIM with a valid MSISDN, both for the reservation of the MSISDN (regulators such as the ITU assign ranges of MSISDN numbers to operating companies) and for the retail staff time and overheads in registering the selected number for use.
Where that SIM appears no longer (or never to have been) used for a predetermined period, the network operators typically note this fact and initiate a “quarantine” process for returning the telephone number to the set of available numbers. Of course, this quarantining process has an associated cost: so too does reassigning that MSISDN number as ultimately will happen when it is confirmed unused after the quarantine period expires.
As the reader will readily appreciate, the provisioning of SIMs that are infrequently or never used represents a distinct inconvenience to the network operator. This inconvenience is significant even when considering the conventional provision of mobile telephones and data card/modems with SIMs. There is however a current trend to embed or otherwise SIM-enable a far wider range of computing and other electronic goods. For example, PC laptops, ultra-mobile PCs (UMPC), personal digital assistants (PDA), satellite positioning devices, set top boxes (STB), wireless access points (APs) and even onboard vehicle computers may be, and lately often are, fitted with modules that accept SIMs to enable communication over cellular telecommunication networks. Clearly, this trend implies a concomitant increase in the number of unused or infrequently used SIMs and a consequently greater level of disruption to the network operator who wishes to enable such devices.
A further problem arises in relation to the production and management of SIM cards for telematics terminals (e.g. in-car computers), where it is desirable that the terminals may be exported to a variety of geographical locations each with their own telecommunication network.
As described in prior patents GB2378097, GB2378094 and GB2378095, the problem may be addressed by ensuring that all relevant operator keys and specific parameters are pre-stored on the SIM, at the time of manufacture. Consequently, a suitably prepared SIM can be re-registered from one home network to another home network as necessary. The SIM is sent instructions regarding which authentication keys it is to use in which territory and a corresponding new SIM identifier number, IMSI.
As a result, where cars are exported, SIMs can be configured for the country of manufacture and later reconfigured for the final country. The method can also apply to other devices and can be indefinitely re-configured. Hence a terminal can be used in another network (not as a roaming subscriber) for a significant time without a new SIM card being issued. Clearly the non- or infrequent use of such “prefitted” SIMs would only amplify the problems outlined above, since this solution requires the provisioning of a plurality of available MSISDNs, one for each territory envisaged at manufacture.
In co-pending UK patent application GB 0805964.4, a new method and system are proposed to address some of the issues above. In this solution, data communications sessions can be established for terminals having identification modules that have only IMSI numbers (and not MSISDN numbers) (thereby sidestepping the need for provisioning or quarantining of SIMs). This is achieved by introducing additional network elements that can identify terminals with such identification modules and handle their requests for data sessions in a consistent way. The system of GB 0805964.4 is primarily suited to data-only communications.
However, there are circumstances where a temporary “return” communications path might be attractive in association with an otherwise data-only service. This could be a telephony service (e.g. CS voice, SMS, USSD, MMS etc) where the server initiates the communication to the client device. An example of such circumstances in telematics might be the need for communications from a telematics service provider to a particular telematics client necessitated by malfunction or abnormal usage patterns. Conventionally routing messages in this direction would require a unique telephone number, such as the MSISDN associated with each SIM.
In such circumstances, the disadvantages of using SIMs with their provisioned MSISDN remain: the provisioning and quarantining of these SIMs to terminals that never need this return channel would make offering a service to all devices prohibitively expensive.